Shop music on Google Play and listen instantly using the Google Play Music app.
The Google Play Music app lets you listen to your music collection anywhere. All your music is stored online, so no need to worry about syncing or storage space.
* Music purchases from Google Play automatically appear in the app.
* Add up to 20,000 more songs from your personal music collection on your computer for free.
* Access your entire music library instantly with the Google Play Music app, and save your favorites for offline playback.
* Share a free full play of the songs you purchase from Google Play with your friends on Google+.
* Learn more about Google Play at http://play.google.com/about/
* Available in the U.S. only.

oh, that's interesting, can't see any options to store music in cloud though.
No, not something you can do yet, well apart from uploading to your google drive yourself etc.
Will be nice when Google music is rolled out to the UK. 20.000 tracks was it? - that should be enough, just have to sort through all my music and whittle out 20thous. Favorited